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The large intestine, or colon is the last part of digestive system: the final stage of the alimentary canal in vertebrate animals. It is the organ where most liquids and minerals are absorbed from digested food, as well as a few remaining nutrients. The large intestine starts in the right iliac region of the pelvis, just at or below the right waist. Near its top, a narrow connecting tube, called the cecum, joins the beginning of the colon to the bottom end of the small intestine. The colon is about 1.5 meters long, which is about one-fifth of the whole length of the intestinal canal. The colon ends at the anus.
Function and relation to other organs In the large intestine, or colon, water is reabsorbed from the chyme. Salts are actively transported from the large intestine, and water follows by osmosis, leaving dense feces. The feces are mainly undigested roughage; they are squeezed by muscle contractions of the colon down to the rectum. There the feces are stored until they are eliminated via the anus. The most obvious difference between the small intestine and the large intestine is that the large intestine is wider. The colon is also more fixed in position and has a sacculated form. It also has certain appendages to its external coat, called the appendices epiploicæ, as well as the better known vermiform appendix, which attaches to the very top end of the colon. The large intestine's muscle fibers are also different from the small intestine: these small muscles do not form a continuous layer around the gut, but are arranged in three longitudinal muscular bands or tæniæ. Also different, the colon has no attachment to any gland (ignoring the disputed appendix). Parts and location The large intestine extends from the front top right of the pelvis or ileum, to the back rear center, or anus. Its route through the pelvis forms the shape of an arch that surrounds the convolutions of the small intestine. It is divided into four major parts; in order from the small intestine, they are the: It has attached the: as well as several intestinal nerves, arteries, and veins. The colon is widest at its start, near its juncture with the cecum. Its diameter gradually diminishes down to the rectum, at which point it becomes considerably narrower just above the anal canal. The large intestine ascends from its beginning through the right lumbar and right hypochondriac regions to the under-surface of the liver. At the liver, it takes a bend to the left, called the right colic flexure, and then transverses the abdomen on the confines of the epigastric and umbilical regions, to the left hypochondriac region. It then bends again, this bend called the left colic flexure, and descends through the left lumbar and iliac regions to the bottom of the pelvis, where it forms a bend called the sigmoid flexure; from this it is continued along the posterior wall of the pelvis to the anus. | |||||||||||||||||||||||||
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